125 



10. The flask, during the operation, is kept immersed 

 in water in a jar (.1), in order to avoid variations in the 

 temperature of the liquid. The results should agree 

 within 0.01. 



11. A convenient method for cleaning the apparatus is 

 as follows: The flask is inverted over a large vessel, 

 preferably a glass jar, and shaken vertically until the 

 liquid starts to flow freely ; it is then held still in a vertical 

 position until empty; the remaining traces of cement can 

 be removed in a similar manner by pouring into the flask 

 a small quantity of clean liquid and repeating the opera- 

 tion. 



Fineness. 



12. Apparatus: The sieves should be circular, about 20 

 cm. (7.87 in.) In diameter. 6 cm. (2.36 in.) high, and pro- 

 vided with a pan. 5 cm. (1.97 in.) deep, and a cover. 



13. The wire cloth should be woven (not twilled) from 

 brass wire having the following diameters: 



No. 100, 0.0045 in.; No. 200, 0.0024 in. 



14. This cloth should be mounted on the frames with- 

 out distortion; the mesh should be regular in spacing and 

 be within the following limits: 



No. 100, 96 to 100 meshes to the linear In. 

 No. 200. 188 to 200 



15. Fifty gram. (1.76 oz.) or 100 gr. (3.52 oz.) should be 

 used for the test, and dried at a temperature of 100 C. 

 (212 F.) prior to sieving. 



16. Method: The thoroughly dried and coarsely screened 

 sample is weighed and placed on the No. 200 sieve, which, 

 with pan and cover attached, is held in one hand in a 

 slightly inclined position, and moved forward and back- 

 ward, at the same time striking the side gently with the 

 palm of the other hand, at the rate of about 200 strokes 

 per minute. The operation is continued until not more 

 than one-tenth of 1 per cent passes through after one 

 minute of continuous sieving. The residue is weighed, 

 then placed on the No. 100 sieve and the operation re- 

 peated. The work may be expedited by placing in the 

 sieve a small quantity of large shot. The results should 

 be reported to the nearest tenth of 1 per cent. 



